Abrasive article



July 1944- F. KEELERIC 2353 404 ABRAS IVE ARTICLE Filed Jan. 1, 19 1s ATTORNEYS 7 Patented July 11, 1944 ABBASIVE ARTICLE George F. Keeleric, Westboro, Mass. Application January 1, 1943, Serial No. 411,035

8 Claims. (01. s1.-3o9) This invention relates to abrasive tools which comprise a tool \body or blank having a layer of speeds, they must be carefully constructed so that they will be in balance and run true, and

this is especially important in the case of tools in the form of wheels of large diameter, because of the vibration that would result from lack of balance. For this reason, the production 01 tools of large diameter having metal bodies is 9. 111111- cult operation and the cost of such tools is correspondingly high.

The present invention is directed to the provision of a novel abrasive tool which offers important advantages over tools tor similar purposes as heretofore made, in that it is lighter in weight and made of less costly materials and, in addition, true running tools oi! the new construction can be made by the new method more easily and at less cost-than prior tools.

The abrasive tool of the-invention comprises a tool body made'of hardened plastic material, abrasive particles partially embeded in the working surface of the body, and bonding material which encircles the particles and lies in contact with'and covers those portions of the working surface of the body lying among the particles. In making the tool by the new method, the particles are first placed in-a mounting having the same form as the working surface of the final tool, the particles being so mounted as to have portions exposed. Thereafter, bonding material is applied to the exposed portions of the particles and the mounting is removed, the particles being thereupon held in place only by the bonding material and having exposed portions which were previously held in the mounting. Plastic material is then applied to enclose the exposed portions or the particles and to contact the bonding More particularly, the

material among the particles. The plastic ma-' terial is caused to harden and, after suitable finishing operations, the tool is completed.

Fora better understanding of the invention,

reference maybe had to the accompanying draw m in which I v i Fig. 1 is aview in perspective of a blank which type. The bonding material has portions lying 7 forms part of a mounting for the abrasive particles;

Fig. 2 is a, fragmentary plan view showing the application of a coating to the peripheral working surface of the blank shown in Fig. 1;

Fig. 31s a view similar to Fig. 2 but with parts broken away showing the mounting of th particles on the blank; v

Fig. 4 is a plan view with parts broken away showing the step of applying bonding material to the particles in the mounting;

Fig. 5 is a fragmentary plan view with parts broken away showing the enclosure in a cast of the mounting carrying the particles;

Fig. 6 is a. view similar to Fig. 5 showing the removal oi the mounting; I

Fig. 7 is a view similar to Fig. 6 showing the formation of a tool body, within the group of particles held together by the bonding material in the cast;

Fig. 8 isa plan view with parts broken away The drawing illustrates the various steps in the new process as employed in the production of the tool shown in Fig. 9, which includes a tool blank or body 20 in the form of a fiat disc having abrasive particles 2! embedded in its peripheral surface. In this figure and elsewhere throughout the drawing, the size of the particles has been greatly and disproportionately exaggerated, so that the construction of the tool and the steps of the process in making it may be made clear.

It is to be understood that the particles employed will vary somewhat in size, depending on the purpose for which the tool is to be employed,

and in the case of diamond particles, for example, the particles may vary from about to 600 mesh.

The body 20 of the new tool is a hardened plas-.

tic material, such as that commercially known as "Bakelite," and the particlesfll are partially embedded in the periphery of the body. The particles arealso held together by a layer 22 of bonding material, which is preferably a hard material, such as iron, nickel, or chromium or successive layers oi diflerent materials of this among the particles and in direct contact with the tool body IQ and it encircles each particle so as to hold the latter firmly in place. By making the tool body of plastic material, the weight of the tool may be relatively small, as compared with prior tools of the same size made'with a metallic body. Also, by forming the tool body of hardened plastic-material by the method to be described, it is comparatively simple to insure the production of true running tools.

In producing tools in accordance with the new method, there is first prepared a forming blank 23 which may be made of any suitable material and is of the same shape and size as the final tool. This blank is preferably made of steel and the first step in the manufacture of tools by its use is the application to the surface thereof corresponding to the working surface of the tool, of a thin layer of relatively soft material which has a lower fusion point than the material of which the forming blank is made. Lead may be used for the layer 24 and it may be applied by electrodeposition, spraying, etc. Non-metallic materials may also be used, such as waxes and plastics, but I prefer to employ lead because it is electroconductive besides being soft andof relatively low melt point. If desired, the entire forming blank may be made of lead or of a relatively soft material of low melt point, but this would require formation of a new forming blank for each tool made and would give rise to other objections.

The blank with its soft peripheral coating serves as a mounting for the abrasive particles during certain succeeding operations and the particles are placed in the mounting by spreading the particles on a flat surface in the desired distribution and then rolling the blank over the layer of particles until the particles are partially embedded in the coating. The depth to which the particles are thus embedded will to an extent determine the exposure of the particles on the working surfaceof the. ultimate tool and the thickness of the layer is, therefore, important, since the particles can be forced wholly through the layer by pressure but will not penetrate the harder forming blank. If the entire blank were made of soft material, the extent of embedding of the particles could be regulated by the degree of pressure employed in embedding them, but this operation would be more difficult to control and that is another reason why the use of a hard forming blank carrying a soft layer is preferred. After the mounting of the particles in the layer, bonding metal is applied, preferably by electrodeposition, although spraying may also be used. The bonding layer 25 builds upon the portions of the surface of layer 24 exposed between. the.

particles and, if the particles have been preliminarily coated with an electro-conductive material, such as a metal, the bonding layer may build up over the portions 26 of the particles and enclose them, as shown in Fig. 4. After the bonding layer has been built up to the desired thickness, the forming blank with the bonded particles thereon, is enclosed within a cast 21 which may be of any suitable material capableof hardening by application of heat. This frees the forming blank 23 and it may be readily slipped out from within th layer of abrasive particles held together by the bonding material.

After removal of the formingblank, the portions of the particles exposed within the interior of the cast may be given a metal coating'by spraying or electrodeposition to improve the withdrawal of heat from the particles during grinding. This operation is unnecessary, if metal coated particles are used. Following the application of metal to the portions of the particles exposed within the interior of the cast, if such a coating is to be used, plastic material 28, which is to form the body 20 of the tool, is introduced into the interior of the cast and caused to fill the crevices between adjacent particles. The operations employed in forming the tool body from such plastic will depend on the character .of the plastic used, but will usually involve the application of heat and pressure.

When the tool body 20 has been formed and has hardened, the cast is removed and the tool is then complete except for finishing operations. Ordinarily the bonding material 25 will have been applied in such a way that it coats the particles to an undesirable extent and some of the bonding material must then be removed in order to give the particles the desired exposure at the working surface of the tool. For this purpose, the bonding material may be plated off or dissolved, the former method. being preferred because of the control of the operation afiorded.

In the completed tool, the particles are held in place partly by being embedded in the tool body 20 and partly by the layer of bonding material which fills the spaces between. the particles and encircles each particle- Particles mounted in this manner are held firmly in position and are not readily dislodged in the use of the tool.

By forming the body of the tool of plastic material while the layer of bonded particles is held rigidly in place within the cast, it is relatively simple to make a tool body which is closely similar to the forming blank 23 and properly balanced, so that it will run true. The molding of the body around the particles insures that they will be firmly embedded therein and the use of plastic in place of metal for the tool body greatly reduces the weight of the tool which is a matter of considerable importance, particularly in tools of large size.

In the foregoing, I have described the utilization of the new method in the formation of a side-cutting wheel but it will be apparent that the usefulness of the method is not limited to the production of grinding instruments of any par- .ticular form. Changes in the method may be necessary in'the production of tools of various types, as, for example, in the formation of an end-cutting tool, the particles will not be rolled into the soft coating on the blank but will be distributed over the layer and forced into the latter in any appropriate way, as by a pressure plate. Such minor modifications of the new method as may be necessary in producing tools of various kinds will be readily apparent from a consideration of the description of the use of the method in the production of the side-cutting tool, set forth above.

I claim:

1. A method of making abrasive tools which comprises placing abrasive particles in a mounting, the particles having portions exposed outside the mounting. applying a bonding material to form a layer coveringthe exposed portions of the particles and the face of the mounting among the particles, removing the mounting from around the particles, and, while the particles are held in place by the bonding layer, forming a tool body in contact with the bonding layer among the particles and enclosing the portions of the particles formerly held in the mounting.

2. A method of making abrasive tools which comprises placing abrasive particlesin a mounting, the particles having portions exposedoutside the mounting, applying. a bonding'material to form a layer covering the exposed portions of bonding material alone, and forming a tool body in contact with the bonding layer among the particles and enclosingv the portions of the particles v formerly held in the mounting.

6. A method of making abrasive tools which comprises applying to the surface of a blank 9. layer of material more readily fusible than that of which the blank is made, embedding abrasive particles in the layer, the particles having portions exposed outside the layer, applying a bonding material to form a layer covering the ex- ,posed portions of the particles and the face of the particles and the face of the mounting among of the particles formerly held in the mounting.

3. A method of making abrasive tools which comprises placing abrasive particles in a mounting, the particles having portions exposed outside the mounting, applying-a bonding material to form a layer covering the exposed portions of the particles and the face of the mounting among the particles, removingthe mounting from around the particles, the particles being then held in place by the layer of bonding material alone, forming a tool body in contact with the bonding layer among the particles and enclosing the portions of the particles formerly held in the mounting, and removing the bonding material coating from the portions of the particles exposed the layer among the particles, removing the blank and the layer of readily fusible material from around the particles, the. particles being then held in place by the layer of bonding material alone, and forming a tool body in contact with the bonding layer among the particles and enclosing the portions of the bodies formerly held comprises applying to the surface of a blank beyond the tool body to a suflicient extent to expose portions of the particles.

4. A method of making abrasive tools which comprises placing abrasive particles in a readily fusible mounting, the particles having portions exposed outside the mounting, applying a bonding material to form a layer covering the exposed portions of the particles and the face of the mounting among the particles, melting the mounting and thereby removing it, the particles being then held in place by the layer of bonding material alone, and forming a tool body in contact with the bonding layer among the particles and enclosing the portions of the particles formerly held in the mounting.

5. A method of making abrasive tools which comprises embedding abrasive particles in a mounting by pressure, the particles having portions exposed outside the mounting, applying a bonding material to form a layer covering the exposed portions of the particles and the face of the mounting among the particles, removing the mounting from around the particles, the particles being then held in place by the layer of in the mounting. a

7. A method of making abrasive tools which a layer of material more readily fusible than that of which the blank is made, embedding abrasive particles in the layer, the particles having portions exposed outside the layer, applying a bonding material to form a layer covering the exposed portions of the particles and the face of the mounting among the particles, placing the blank in a cast with the layer of bonding material and the portions of the particles covered thereby embedded in the cast material, removing the blank and the layer of readily fusible material from around .the particles while the latter and the bonding material remain in the cast. forming a tool body in contact with the bonding layer among the particles and enclosing the portions of the particles formerly'held in the mounting, and removing the cast.

8. 'A method of making abrasive tools which comprises applying to a blank a coating of a material more fusible than that of which the blank is made, embedding abrasive particles in the layer, the particles having portions exposed outside the layer, coating the exposed portions of the particles and the portions of the layer between them with a bonding material, mounting the blank in a cast with the cast material contacting with the exposed surface of the bonding material and enclosing the portions of the particles lying outside the layer, removing the blank and the layer from around the particles, forming a tool body in contact with the bonding layer among the particles and enclosing the portionsof the particles previously embedded in the layer, removing the cast, and removing the bonding material coating from the portions of the particles exposed beyond the tool body to a suflicient extent to expose portions of the particles,

1 GEORGE F. KEELERIC. 

